This is a quick update on the T-SQL exercise I posted a few days ago. The goal was to write a simple T-SQL script to generate and load 4,000,000 rows into a table so that the following query would produce the worst performance, i.e. take longest time to finish:
DBCC DROPCLEANBUFFERS
go
SELECT COUNT(*) FROM dbo.test;
The ...

Here is a T-SQL scripting exercise in case you have a few minutes to spare or are bored with whatever else you are doing.
Objective
The task is to write a simple T-SQL script to generate and load 4,000,000 rows into a test table. The objective is to make the following simple test query to have the worst performance in terms of ...

This came out on the Microsoft website. I have not had time to look over the hardware configuration carefully. Of course the recommended storage is a SAN, vendors love to sell very high margin products when there are perfectly good merely high margin alternatives. Well atleast this one looked at sequential disk IO bandwidth, unlike past ...

SQL Server workloads
So far, the discussions in all the previous posts (1, 2, 3, and 4) on the performance impact of file fragmentation on a drive presented from a high-end enterprise-class disk array are related to disk I/O workloads. Ultimately, you want to know how file fragmentation may impact your SQL Server workloads.
In ...

Lies, damned lies, and statistics!
If you have read my three previous posts (1, 2, 3), you may walk away with an impression that on a drive presented from a high-end enterprise class disk array, Windows file fragmentation does not have a significant performance impact. And I’ve given you empirical data—oh yeah, statistics—to support that ...

256KB Sequential Reads
In my two previous posts (1, 2), I highlighted the fact that while file fragmentation had a huge adverse performance impact on directly attached storage (DAS), it did not have much, if any, impact on the drive presented from a high end enterprise class disk array. That observation was derived from running disk I/O ...

1KB Sequential Writes on DAS
There were some questions about the use 1KB sequential writes in my previous post to test the performance impact of file fragmentation on a drive presented from a high end enterprise class disk array.
There were two reasons for testing 1KB sequential writes:
· SQL ...

1KB Sequential Writes
It’s well known that disk I/O performance can be severely impacted by fragmentation at the file system level. In other words, when a file is allocated space from many small fragments, its performance can be much worse than when its space is allocated from a single contiguous chunk. The impact is most pronounced with ...

There were discussions on disk misalignment on this site. See my previous post on “Performance Impact of Disk Misalignment”, and Kevin Kline’s blog on “How to Improve Application and Database Performance up to 40% in One Easy Step”
But thanks to Jimmy May's PASS 2008 presentation on the I/O performance impact of disk partition ...

Last month, Scott pointed out the really bad performance characteristics of the Dell PERC6 in RAID0 sequential write, particularly compared with RAID-5. Granted, this is not necessarily a red flag because few people use RAID 0 in production. Still, if one can't write code or test correctly, one should not be in the hardware/firmware business. Dell ...